There are more bacterial cells present in and on the body than the number of human cells with the gut microbiota having the largest number of bacteria and the most diversity. The human gastrointestinal microbiota is the name given to the microorganisms that live in the digestive tracts of humans. Microbiota varies according to their surrounding environment.
The gut flora establishes itself in the first few weeks after birth and has various roles on human health. In humans, the gut microbiota usually establishes itself about one to two years after birth. The delivery mode of the baby can also influence and shape the microbiota. This is usually the time that the intestinal mucosal barrier and intestinal epithelium of the newborn are developed. The mutualistic relationship between the host and the gut microbiota is very prominent, as the intestine is developed in a way to aid the growth of the gut microorganisms.
Approximately 100 trillion micro-organisms (most of them are bacteria, but also viruses, fungi, and protozoa) exist in the human gastrointestinal tract- the microbiome is now best thought of as a virtual organ of the body. The human genome consists of about 23, 000 genes, whereas the microbiome encodes over three million genes producing metabolites, they replace many of the functions of the host, consequently influencing the host’s fitness, phenotype, and health.
The gut flora has multiple functions that make it extremely beneficial to the host such as inhibition of pathogens, enhancing the host immune system and metabolizing indigestible compounds in food. The inhibition of pathogens is done by the entire gut flora community by colonizing all the space and making use of all the nutrients available. They also secrete compounds that directly inhibit unwanted organisms that may want to compete for their resources.
A person’s diet is one of the main determinants of the composition of the gut flora. Different genera of bacteria are associate with different nutrient intake. The association and concentration between each microbial community depend on the type of diet consumed. People of different geographical regions show significant differences in thein git flora composition. The dominating enterotype in the gut flora is almost similar in most people in the same region indicating that it depends on the regional conditions.
Your gut and brain are connected by the vagus nerve, a major component of the autonomic nervous system which enables you to breathe, digest food, and swallow automatically. This nerve can send messages to your brain for your colon, and vice versa. The connection between the two organs means that the gut-brain axis is becoming a vital player in mental health, illnesses that affect the brain, and even irritable bowel syndrome (IBS). It explains why stress can take a toll on your digestion but also why digestive problems can make you unhappy.
Gut bacteria break down food, particularly dietary fibre and transform it into metabolites like short-chain fatty acids (SCAFs). These are detected by the nerve which then sends data to the brain, allowing the regulation of digestive processes. On the other hand, when the vagus nerve is impaired by stress (that directs energy and attention to your muscles and brain), it can’t react effectively to inflammation, which is bad for your gut and your gut bacteria. And that’s why your vagus nerve is so important.